[dinosaur] Hesperornithiforms as Environmental Indicators in Late Cretaceous Western Interior Seaway

Ben Creisler
[email protected]

A new paper:

Laura E. Wilson (2019)
A Bird's Eye View: Hesperornithiforms as Environmental Indicators in the
Late Cretaceous Western Interior Seaway.
Transactions of the Kansas Academy of Science 122(3-4): 193-213
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1660_062.122.0302&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=-VcirOo0mr_IgM8sCHUO3v0zmHcVXGlXz-57TNBqmFw&s=Ol3-QLWfIPZV3i30wVR3AQORaTkT9WFcjT2CK2OM8yw&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__bioone.org_journals_Transactions-2Dof-2Dthe-2DKansas-2DAcademy-2Dof-2DScience_volume-2D122_issue-2D3-2D4_062.122.0302_A-2DBirds-2DEye-2DView-2D-2DHesperornithiforms-2Das-2DEnvironmental-2DIndicators-2Din_10.1660_062.122.0302.short&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=-VcirOo0mr_IgM8sCHUO3v0zmHcVXGlXz-57TNBqmFw&s=573fJ51AIHK6L0K2PrL_34RFZRv31HtpWzJ50wMlH4c&e= 


Seabirds are considered indicators of ecological hotspots in modern
ecosystems because their biogeographic distribution is correlated with
physical, chemical, and biological oceanographic factors. Pursuit diving
seabirds – those that actively pursue prey underwater – are generally more
limited in distribution and more closely tied to oceanographic factors, as
diving ability is often gained at the expense of flight capabilities.
Today, wing propelled pursuit diving seabirds are restricted to colder
waters; foot propelled divers have a broader latitudinal distribution, but
do not forage far from shore in marine environments. In comparison, Late
Cretaceous Northern Hemisphere seas were host to foot propelled pursuit
diving seabirds called hesperornithiforms. Their Western Interior Seaway
fossil record, in particular, reflects the broad latitudinal distribution
of modern foot propelled divers, but with occurrences of offshore foraging
more typical of modern wing propelled divers. The presence of
hesperornithiforms in such a wide variety of environments (Boreal, Tethyan,
coastal, nearshore, and offshore) suggests different ecological and
oceanographic conditions affected biogeographic patterns of Late Cretaceous
divers. The purpose of this study is to explore Late Cretaceous
hesperornithiform paleobiogeography in light of what is known about how
biotic and environmental factors affect modern pursuit diving seabirds to
better understand WIS paleoecology.

The Late Cretaceous was characterized by greenhouse climate, high sea
levels, and epicontinental seas that provided marine paleoenvironments with
no modern analogs. Two notable ecological differences between the Late
Cretaceous and today are the presence of marine reptiles (and absence of
marine mammals) as apex predators and the lack of acanthomorph fish
diversity. Spatio-temporal overlap among hesperornithiforms, marine
reptiles, and large predatory fishes implies different competition and
predator-prey relationships among marine carnivores than today. Differences
in swimming capabilities between marine reptiles and marine mammals may
partially account for the presence of hesperornithiforms in warm, offshore
waters. Additionally, environmental factors relating to the unique
paleoceanography of the WIS would have also influenced hesperornithiform
populations. Ample shoreline, abundant shallow water habitats, and high
primary production made epicontinental seas hotspots for pursuit diving
seabirds, despite warmer temperatures. Together, ecosystem structure and
the unique oceanographic factors characterizing epicontinental seas both
contribute to differences in seabird biogeography between the Late
Cretaceous and today.